import java.util.Stack;

public class Offer_31 {
    /**
     * 剑指 Offer 31. 栈的压入、弹出序列
     * 输入两个整数序列，第一个序列表示栈的压入顺序，请判断第二个序列是否为该栈的弹出顺序。假设压入栈的所有数字均不相等。例如，序列 {1,2,3,4,5} 是某栈的压栈序列，序列 {4,5,3,2,1} 是该压栈序列对应的一个弹出序列，但 {4,3,5,1,2} 就不可能是该压栈序列的弹出序列。
     */

    public static boolean validateStackSequences(int[] pushed, int[] popped) {
        //如果两个都等于零的话，返回true
        if (pushed.length == 0 && popped.length == 0) {
            return true;
        }
        if (pushed.length == 0 || popped.length == 0 || pushed.length != popped.length) {
            return false;
        }
        Stack<Integer> tempStack = new Stack<>();
        int j = 0;
        for (int i = 0; i < pushed.length; i++) {
            tempStack.add(pushed[i]);
            while (!tempStack.isEmpty() && tempStack.peek() == popped[j]) {
                tempStack.pop();
                j++;
            }
        }
        return tempStack.isEmpty();
    }

    public static void main(String[] args) {
        int[] pushed = {1, 2, 3, 4, 5};
        int[] popped = {4, 5, 3, 2, 1};
        System.out.println(validateStackSequences(pushed, popped));
    }
}
